1. Field of the Invention
The present invention relates to a photomultiplier and, more particularly, to an electron muitlplier for constituting the photomultiplier and cascade-multiplying an incident electron flow or ions by multilayered dynodes.
2. Related Background Art
In a conventional electron multiplier, a plurality of dynodes are multilayered at predetermined intervals to constitute a dynode unit for cascade-multiplying an incident electron flow. In U.S. Pat. No. 3,229,143, insulating balls are inserted between dynodes to constitute a dynode unit. FIG. 1 shows the main part of this structure. A through hole 103 is formed in each support plate 101 for supporting the corresponding stage of dynodes. An insulating ball 102 having part thereof fit in the opening ends of each through hole 103 is inserted between each pair of support plates 101. The insulating ball 102 is formed of pyrex and has a diameter larger than the inner diameter of the through hole 103. On the other hand, the through hole 103 forms a cylindrical hole having a predetermined inner diameter.